1. Field of the Disclosure
The present disclosure relates to a sending magnet apparatus for motor.
2. Discussion of the Related Art
Generally, almost every vehicle employs an electric power-assist steering system. Such an electric power-assist steering system generates an assist force based on the steering torque and the steering angle, so as to enhance the steering performance of the vehicle.
That is, a steering system that assists a steering force of a vehicle with a separate power is used to enhance the motion stability of a vehicle.
Conventionally, the auxiliary steering device uses hydraulic pressure, but an Electronic Power Steering (EPS) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a viewpoint of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is configured such that an Electronic Control Unit (ECU) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The EPS system is also configured such that a motor assists a torque manipulating a steering wheel to allow a driver to steer a vehicle with less power, where the motor employs a Brushless Direct Current (BLDC) motor.
The BLDC motors have been increasingly used because the brushless motors are excellent in maintenance property, have a small size, and are capable of generating a high torque.
The BLDC motor generally forms an exterior look by coupling of a housing and a cover member, where an inner circumferential surface of the housing is provided with a stator, and the stator is centrally formed with a rotor rotatably mounted in electrical interaction with the stator. The rotor is rotatably supported by a rotation shaft, and an upper surface of the rotation shaft is connected by a steering shaft of a vehicle to provide a power assisting the steering of the vehicle as mentioned above.
Meanwhile, the cover member is installed at an inner side with a PCB (Printed Circuit Board) mounted with a detecting sensor provided by a magnetic element. The detecting sensor serves to detect a magnetic force of a sensing magnet rotatably mounted with the rotor to learn a current position of the rotor. Generally, the sensing magnet is fixed to an upper surface of a plate mounted at an upper surface of the rotor using an adhesive. In a case the sensing magnet is magnetized to the plate, the plate is coupled to a rotation shaft in tune with a direction of magnetic field to detect a position of the rotor.
Meanwhile, as mentioned above, the plate and the sensing magnet are coupled using an adhesive. Thus, it is difficult to manage an accurate adhering process, whereby the sensing magnet may be easily dislodged. Particularly, in view of vehicular characteristics of varying environmental conditions, and in light of the coupled relationship being maintained only by an adhesive power alone of the adhesive, if the motor is alternatively used in between a high temperature state and a low temperature state, or is exposed to a high temperature state for a long time, the adhesive power of the adhesive deteriorates to cause the sensing magnet to be dislodged or to disable a motor driving.
This structure suffers from a difficulty in selecting a right adhesive, leading to an economic problem of using a high cost adhesive, and a more accurate operation in adhesive coating processing. Furthermore, in a case the plate and the sensing magnet are being pressed while the adhesive is coated on a flat surface of a magnet, or in a case an adhesive is thickly coated, the adhesive coated on the surface of the magnet may leak out of an adhered part, or an excessively thick adhesive layer may be formed to cause a Hall element and a sensing magnet to be excessively closely arranged or to be mutually interfered.